/*******************************************************************************
 * Copyright 2011, 2012 Chris Banes.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *******************************************************************************/
package com.videogo.widget.pulltorefresh;

import android.annotation.TargetApi;
import android.view.View;

import com.videogo.util.LogUtil;
import com.videogo.widget.pulltorefresh.IPullToRefresh.Mode;
import com.videogo.widget.pulltorefresh.IPullToRefresh.State;

@TargetApi(9)
public final class OverscrollHelper {

    static final String LOG_TAG = "OverscrollHelper";

    static final float DEFAULT_OVERSCROLL_SCALE = 0.5f;

    /**
     * Helper method for Overscrolling that encapsulates all of the necessary function.
     * <p/>
     * This should only be used on AdapterView's such as ListView as it just calls through to
     * overScrollBy() with the scrollRange = 0. AdapterView's do not have a scroll range (i.e.
     * getScrollY() doesn't work).
     * 
     * @param view
     *            - PullToRefreshView that is calling this.
     * @param deltaX
     *            - Change in X in pixels, passed through from from overScrollBy call
     * @param scrollX
     *            - Current X scroll value in pixels before applying deltaY, passed through from
     *            from overScrollBy call
     * @param deltaY
     *            - Change in Y in pixels, passed through from from overScrollBy call
     * @param scrollY
     *            - Current Y scroll value in pixels before applying deltaY, passed through from
     *            from overScrollBy call
     * @param isTouchEvent
     *            - true if this scroll operation is the result of a touch event, passed through
     *            from from overScrollBy call
     */
    public static void overScrollBy(final PullToRefreshBase<?> view, final int deltaX, final int scrollX,
            final int deltaY, final int scrollY, final boolean isTouchEvent) {
        overScrollBy(view, deltaX, scrollX, deltaY, scrollY, 0, isTouchEvent);
    }

    /**
     * Helper method for Overscrolling that encapsulates all of the necessary function. This version
     * of the call is used for Views that need to specify a Scroll Range but scroll back to it's
     * edge correctly.
     * 
     * @param view
     *            - PullToRefreshView that is calling this.
     * @param deltaX
     *            - Change in X in pixels, passed through from from overScrollBy call
     * @param scrollX
     *            - Current X scroll value in pixels before applying deltaY, passed through from
     *            from overScrollBy call
     * @param deltaY
     *            - Change in Y in pixels, passed through from from overScrollBy call
     * @param scrollY
     *            - Current Y scroll value in pixels before applying deltaY, passed through from
     *            from overScrollBy call
     * @param scrollRange
     *            - Scroll Range of the View, specifically needed for ScrollView
     * @param isTouchEvent
     *            - true if this scroll operation is the result of a touch event, passed through
     *            from from overScrollBy call
     */
    public static void overScrollBy(final PullToRefreshBase<?> view, final int deltaX, final int scrollX,
            final int deltaY, final int scrollY, final int scrollRange, final boolean isTouchEvent) {
        overScrollBy(view, deltaX, scrollX, deltaY, scrollY, scrollRange, 0, DEFAULT_OVERSCROLL_SCALE, isTouchEvent);
    }

    /**
     * Helper method for Overscrolling that encapsulates all of the necessary function. This is the
     * advanced version of the call.
     * 
     * @param view
     *            - PullToRefreshView that is calling this.
     * @param deltaX
     *            - Change in X in pixels, passed through from from overScrollBy call
     * @param scrollX
     *            - Current X scroll value in pixels before applying deltaY, passed through from
     *            from overScrollBy call
     * @param deltaY
     *            - Change in Y in pixels, passed through from from overScrollBy call
     * @param scrollY
     *            - Current Y scroll value in pixels before applying deltaY, passed through from
     *            from overScrollBy call
     * @param scrollRange
     *            - Scroll Range of the View, specifically needed for ScrollView
     * @param fuzzyThreshold
     *            - Threshold for which the values how fuzzy we should treat the other values.
     *            Needed for WebView as it doesn't always scroll back to it's edge. 0 = no
     *            fuzziness.
     * @param scaleFactor
     *            - Scale Factor for overscroll amount
     * @param isTouchEvent
     *            - true if this scroll operation is the result of a touch event, passed through
     *            from from overScrollBy call
     */
    public static void overScrollBy(final PullToRefreshBase<?> view, final int deltaX, final int scrollX,
            final int deltaY, final int scrollY, final int scrollRange, final int fuzzyThreshold,
            final float scaleFactor, final boolean isTouchEvent) {

        final int deltaValue, currentScrollValue, scrollValue;
        switch (view.getPullToRefreshScrollDirection()) {
            case HORIZONTAL:
                deltaValue = deltaX;
                scrollValue = scrollX;
                currentScrollValue = view.getScrollX();
                break;
            case VERTICAL:
            default:
                deltaValue = deltaY;
                scrollValue = scrollY;
                currentScrollValue = view.getScrollY();
                break;
        }

        // Check that OverScroll is enabled and that we're not currently
        // refreshing.
        if (view.isPullToRefreshOverScrollEnabled() && !view.isRefreshing()) {
            final Mode mode = view.getMode();

            // Check that Pull-to-Refresh is enabled, and the event isn't from
            // touch
            if (mode.permitsPullToRefresh() && !isTouchEvent && deltaValue != 0) {
                final int newScrollValue = (deltaValue + scrollValue);

                if (PullToRefreshBase.DEBUG) {
                    LogUtil.debugLog(LOG_TAG, "OverScroll. DeltaX: " + deltaX + ", ScrollX: " + scrollX + ", DeltaY: " + deltaY
                            + ", ScrollY: " + scrollY + ", NewY: " + newScrollValue + ", ScrollRange: " + scrollRange
                            + ", CurrentScroll: " + currentScrollValue);
                }

                if (newScrollValue < (0 - fuzzyThreshold)) {
                    // Check the mode supports the overscroll direction, and
                    // then move scroll
                    if (mode.showHeaderLoadingLayout()) {
                        // If we're currently at zero, we're about to start
                        // overscrolling, so change the state
                        if (currentScrollValue == 0) {
                            view.setState(State.OVERSCROLLING);
                        }

                        view.setHeaderScroll((int) (scaleFactor * (currentScrollValue + newScrollValue)));
                    }
                } else if (newScrollValue > (scrollRange + fuzzyThreshold)) {
                    // Check the mode supports the overscroll direction, and
                    // then move scroll
                    if (mode.showFooterLoadingLayout()) {
                        // If we're currently at zero, we're about to start
                        // overscrolling, so change the state
                        if (currentScrollValue == 0) {
                            view.setState(State.OVERSCROLLING);
                        }

                        view.setHeaderScroll((int) (scaleFactor * (currentScrollValue + newScrollValue - scrollRange)));
                    }
                } else if (Math.abs(newScrollValue) <= fuzzyThreshold
                        || Math.abs(newScrollValue - scrollRange) <= fuzzyThreshold) {
                    // Means we've stopped overscrolling, so scroll back to 0
                    view.setState(State.RESET);
                }
            } else if (isTouchEvent && State.OVERSCROLLING == view.getState()) {
                // This condition means that we were overscrolling from a fling,
                // but the user has touched the View and is now overscrolling
                // from touch instead. We need to just reset.
                view.setState(State.RESET);
            }
        }
    }

    static boolean isAndroidOverScrollEnabled(View view) {
        return view.getOverScrollMode() != View.OVER_SCROLL_NEVER;
    }
}
